Electric passenger vehicles powered by batteries have been reintroduced in the United States. Although there are no tailpipe emissions associated with electric vehicles, charging the batteries requires power with which there are associated emissions. However, emissions from large sources are relatively easier to control than from millions of individual automobiles. In addition, the emissions of VOCs and CO from power plants are generally low, while those of NO,, S02, and particles depend on the type of fuel used. Natural gas-fired power plants generally have relatively low S02 and particle emissions, whereas coal-fired power plants have higher emissions of these pollutants and of NO,. Studies by Austin described by Cadle et al. (1996) suggest that the use of electric vehicles would result in lower total emissions of NO, in the western United States, where gas is used at power plants, but higher emissions in the east, where coal is used. Larger PM10 and S02 emissions were projected regardless of the power plant fuel source.
Another version of the electric vehicle that has been introduced into Japan and is scheduled to be introduced into the United States is a hybrid vehicle with both electric and gasoline engines. Such vehicles have the promise of lower emissions and much longer ranges than can currently be achieved with electric vehicles.
For a discussion of various aspects of electric vehicles, see Wilkinson (1997) and the May 1998 issue of Environmental Manager.
ft should be noted that in addition to the change in total emissions, the change in the spatial and temporal nature of the emissions, i.e., replacing many individual sources that are dispersed in time and space by a single source, may also be very important in determining air quality at various locations in an air basin.
Fuel cells, in which a fuel such as methane, gasoline, or methanol is converted to electricity, to power vehicles also appear promising and indeed are currently being used on some buses. For a detailed discussion of this important area, see Lloyd (1992) and Lloyd et al. (1994).
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